ESCO2 is an acetyltransferase required for the establishment of sister chromatid cohesion, and couples the processes of cohesion and DNA replication to ensure that only sister chromatids become paired together. In contrast to the structural cohesins, the deposition and establishment factors are required only during S phase.
Defects in ESCO2 are the cause of Roberts syndrome (RBS), a rare autosomal recessive disorder characterized by pre- and postnatal growth retardation, microcephaly, bilateral cleft lip and palate, and mesomelic symmetric limb reduction. Severely affected infants may be stillborn or die shortly after birth. RBS chromosomes have a lack of cohesion involving the heterochromatic C-banding regions around centromeres and the distal portion of the long arm of the Y chromosome (known as premature centromere separation, heterochromatin repulsion or puffing, or RS effect).
Defects in ESCO2 are also the cause of SC phocomelia syndrome, also known as SC pseudothalidomide syndrome. SC phocomelia syndrome has a milder phenotype than RBS, with a lesser degree of symmetric limb reduction and additionally includes flexion contractures of various joints, midfacial hemangioma, hypoplastic cartilage of ears and nose, scant silvery-blond hair, and cloudy corneae. Although microcephaly is present, mental retardation may be mild and survival into adulthood is common.